A wireless communication apparatus including a terminal, such as a mobile telephone, corresponding to plural communication systems has been used. Such terminal includes plural filters corresponding to different frequency bands of the communication systems. The filters are generally implemented by surface acoustic wave filters, and a surface acoustic wave device including the surface acoustic wave filters is used.
A surface acoustic wave filter disclosed in JP 2006-80921A includes a base substrate, a piezoelectric substrate mounted onto the base substrate by flip-chip, comb electrodes mounted on the piezoelectric substrate, and a sealer made of resin or metallic material for sealing a surface of the piezoelectric substrate.
The base substrate having plural surface acoustic wave filters mounted and sealed thereon has a large size and may receive a large physical stress from the sealer. The stress produces a distortion on the base substrate, and the distortion is transferred to the surface acoustic wave filters mounted on the base substrate by flip-chip, causing inter-modulation (IM) characteristics of the device deteriorate. Particularly being used as transmitting filters, the surface acoustic filters have a large power signal supplied from a power amplifier, accordingly being affected by the deteriorating of the IM characteristics.